Kyosuke HIrayama, Yasuhiro Morizono, Sadahiro Tsurekawa, Yasuyoshi Hidaka, Yonosuke Yoshii, Grain Boundary Engineering of 10% Cr Ferritic-Martensitic Steel SUH3, ISIJ International, 2015.05, Thermomechanical treatments for manipulating grain boundary microstructure in 10 wt%Cr ferriticmartensitic steel SUH3 have been studied. Material with a high fraction of coincidence site lattice (CSL) boundaries was successfully produced and subjected to steam oxidation tests to demonstrate the utility of grain boundary engineering. Introducing a high fraction of twin boundaries in austenite resulted in a significant increase in the number of CSL boundaries along the prior austenite grain boundaries in martensite. In addition, grain boundary engineering introduced a high density of subblock structures in martensite, which resulted in a homogeneous distribution of fine precipitates in tempered martensite. Steam oxidation tests demonstrated that grain boundary engineering for SUH3 steel can achieve enhanced oxidation resistance..

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Kyosuke Hirayama, Seiichiro Ii, Sadahiro Tsurekawa, Transmission electron microscopy/electron energy loss spectroscopy measurements and ab initio calculation of local magnetic moments at nickel grain boundaries, Science and Technology of Advanced Materials, 2014.01, We have determined local magnetic moments at nickel grain boundaries using a transmission electron microscopy/electron energy loss spectroscopy method assuming that the magnetic moment of Ni atoms is a linear function of the L3/L2 (white-line ratio) in the energy loss spectrum. The average magnetic moment measured in the grain interior was 0.55μB, which agrees well with the calculated magnetic moment of pure nickel (0.62μB). The local magnetic moments at the grain boundaries increased up to approximately 1.0μB as the mis-orientation angle increased, and showed a maximum around 50. The respective enhancement of local magnetic moments at the 65 (0.63μB) and random (0.90μB) grain boundaries in pure nickel was approximately 14 and 64% of the grain interior. In contrast, the average local magnetic moment at the (111) 63 grain boundary was found to be 0.55μB and almost the same as that of the grain interior. These results are in good agreement with available ab initio calculations..

平山 恭介, 戸田 裕之, 上杉健太朗, 竹内晃久, Evaluation of Crystallographic Deformation Behavior in Aluminium Alloy by Means of Diffraction-Amalgamated Grain-Boundary Tracking (DAGT) Technique, 3rd International Congress on 3D Materials Science 2016, 2016.07, We proposed new diffraction-amalgamated grain-boundary tracking (DAGT)technique, which was developed by combining the grain boundary tracking (GBT) technique and XRD using a pencil beam. The method provides a description of the crystallographic orientations of individual grains in polycrystalline material during deformation by 4D (3D + time). The main motivation of this study is to verify the plastic deformation behavior on the basis of DAGT technique..

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平山 恭介, 戸田 裕之, 寺岡佑佳子, 上杉健太朗, 竹内晃久, Assessment of deformation behavior in aluminum alloy with Diffraction-Amalgamated Grain-Boundary Tracking (DAGT) technique, The 15th International Conference on Aluminum Alloys, 2016.06, The behavior of individual grain during plastic deformation is affected by shape and size of grains and the crystal orientations for the grains in polycrystalline. We proposed new diffraction-amalgamated grain-boundary tracking (DAGT) technique, which was developed by combining the grain boundary tracking (GBT) technique and a pencil beam XRD. The method provides a description of the crystallographic orientations of individual grains in polycrystalline material during deformation by 4D (3D + time). In addition, the crystal orientation of each grain in plastic deformed material with high strain rate over 20% is determined by means of this technique. Therefore we conducted the assessment of the plastic deformation behavior based on determination of crystal orientation before and after deformation for each grain by using DAGT technique..

平山 恭介, Plastic Deformation Behavior of Aluminum Alloy Investigated Means of Diffraction-Amalgamated Grain-Boundary Tracking (DAGT) Technique, International Conference on Advanced Technology in Experimental Mechanics 2015, 2015.10, The slip plane and direction of individual grain during plastic deformation are affected by crystal orientation for the grain in polycrystalline. So, it is necessary to determine crystal orientation of interior material during deformation by 4D analysis with time in order to understand the plastic deformation behavior. However, 4D analysis for crystal orientation during plastic deformation over 10% has yet been carried out. In this work, the plastic deformation behavior was analyzed based on determination of crystal orientation before and after deformation for each grain by using diffraction-amalgamated grain-boundary tracking (DAGT) technique consisting of grain boundary tracking (GBT) technique and pencil beam XRD. Material used Al-4mass%Cu alloy with grain size of 100m. CT scan was carried out on each step of tensile test. After tensile test, grain boundaries in sample were visualized by Ga doping. In pencil beam XRD, X-ray was reduced into a thinner beam (10m) and irradiated sample during deformation. X ray energy was 35KeV. We achieved to determine crystal orientation before and after deformation for each grain by DAGT technique. The crystal orientations of grains inside sample were also determined. In addition, <111> direction enhanced after tensile test..